Fix handling recursive symlinks

When pytest was run on a directory containing a recursive symlink it failed
with ELOOP as the library was not able to determine the type of the
direntry:

src/_pytest/main.py:685: in collect
    if not direntry.is_file():
E   OSError: [Errno 40] Too many levels of symbolic links: '/home/florian/proj/pytest/tests/recursive'

This is fixed by handling ELOOP and other errors in the visit function in
pathlib.py, so the entries whose is_file() call raises an OSError with the
pre-defined list of error numbers will be exluded from the result.

The _ignore_errors function was copied from Lib/pathlib.py of cpython 3.9.

Fixes #7951

1 files changed, 38 insertions, 1 deletions

diff --git a/src/_pytest/pathlib.py b/src/_pytest/pathlib.py
index f0bdb1481..a1c364076 100644
--- a/src/_pytest/pathlib.py
+++ b/src/_pytest/pathlib.py
@@ -9,6 +9,10 @@ import sys
 import uuid
 import warnings
 from enum import Enum
+from errno import EBADF
+from errno import ELOOP
+from errno import ENOENT
+from errno import ENOTDIR
 from functools import partial
 from os.path import expanduser
 from os.path import expandvars
@@ -37,6 +41,24 @@ LOCK_TIMEOUT = 60 * 60 * 24 * 3
 
 _AnyPurePath = TypeVar("_AnyPurePath", bound=PurePath)
 
+# The following function, variables and comments were
+# copied from cpython 3.9 Lib/pathlib.py file.
+
+# EBADF - guard against macOS `stat` throwing EBADF
+_IGNORED_ERRORS = (ENOENT, ENOTDIR, EBADF, ELOOP)
+
+_IGNORED_WINERRORS = (
+    21,  # ERROR_NOT_READY - drive exists but is not accessible
+    1921,  # ERROR_CANT_RESOLVE_FILENAME - fix for broken symlink pointing to itself
+)
+
+
+def _ignore_error(exception):
+    return (
+        getattr(exception, "errno", None) in _IGNORED_ERRORS
+        or getattr(exception, "winerror", None) in _IGNORED_WINERRORS
+    )
+
 
 def get_lock_path(path: _AnyPurePath) -> _AnyPurePath:
     return path.joinpath(".lock")
@@ -555,8 +577,23 @@ def visit(
 
     Entries at each directory level are sorted.
     """
-    entries = sorted(os.scandir(path), key=lambda entry: entry.name)
+
+    # Skip entries with symlink loops and other brokenness, so the caller doesn't
+    # have to deal with it.
+    entries = []
+    for entry in os.scandir(path):
+        try:
+            entry.is_file()
+        except OSError as err:
+            if _ignore_error(err):
+                continue
+            raise
+        entries.append(entry)
+
+    entries.sort(key=lambda entry: entry.name)
+
     yield from entries
+
     for entry in entries:
         if entry.is_dir(follow_symlinks=False) and recurse(entry):
             yield from visit(entry.path, recurse)